Receptor organs in the coxal region of Palinurus vulgaris
Alexandrowicz, J.S. (1967) Receptor organs in the coxal region of Palinurus vulgaris. Journal of the Marine Biological Association of the United Kingdom, 47 (2). pp. 415-432.
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In the coxal region of Palinurus vulgaris Latr. the following proprioceptors are present: (I) a thoracico-coxal muscular receptor, (2) two innervated elastic strands(depressor and levator receptors), and (3) a coxo-basipodite receptor. Thus, Palinurus has the same number of these organs as some Brachyura and Anomura,but differs from Homarus and Astacus, which have five of them. In all the five thoracic segments carrying the legs the receptor organs inPalinurus originate on special receptor rods which are thin projections of the endophragmal skeleton. The muscle elements of the muscular receptor are surrounded by connective tissue which in the proximal part of the muscle forms a thick sheath. To the receptor rod the muscle is attached by a short tendon. The motor fibres reach the receptor muscle at about the midpoint of its course. Two thick and one thinner sensory fibres are connected with the muscular receptor. One of the thick fibres ends on the tendon, the other thick fibre and the thinner one pass into the connective tissue of the muscle sheath. The depressor receptor consists of one strand and the levator depressor of a main and an additional strand. The main levator strand is distinguished by a particularly rich innervation. The sensory neurons of the muscular receptor and of the innervated elasticstrands have their cell bodies located in the central nervous system. The coxo-basipodite receptor, CB, consisting of an elastic strand and numerous nerve cells, belongs to the same system as the chordotonal organs in other leg joints. It is assumed that the mode of functioning of coxal receptors in Palinurus is the same as in the Brachyura and Anomura, namely the muscular receptor is presumably regulating the leg movements in the horizontal plane and the depressor and levator receptors those in the vertical plane. During the latter movements the CB receptor is probably playing some subsidiary role.
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